Vehicle headlight with movable screen



y 3, 1958 M. afHE'ucl-loz EI'AL I 2,834,874

VEHICLE BEADLIGHT WITH MOVABLE SCREEN Filed March 51, 1954 3Sheets-Sheet l M. E. HENCHOZ ETAL 2,834,874

VEHICLE HEADLIGHT WITH MOVABLE SCREEN Filed March 51, 1954 May 13, 19585 Sheets-Sheet 2 May 13, 1958 M. E. HENCHOZ El'AL 2,834,874

VEHICLE HEADLIGHT WITH MOVABLE SCREEN Filed March 51, 1954 5Sheets-Sheet 5 United States Patent 6 VEHICLE HEADLIGHT WITH MOVABLESCREEN Marcel Edouard Henchoz and Edmond Theophile Dgallier, Lausanne,Switzerland Application March 31, 1954, Serial No. 420,142 Claimspriority, application Switzerland April 1, 1953 8 Claims. (Cl.Mil-46.07)

The present invention relates to a vehicle headlight and is moreparticularly concerned with an adjustable headlight. In accordance withthe invention there is provided a headlight which comprises a parabolicreflector, a source of light positioned at least approximately at thefocus of the reflector, and means for modifying the beam of light raysemitted for the purpose of reducing the blinding or glaring efiectproduced by the beam upon the driver of an approaching vehicle whilestill providing adequate illumination ahead of the vehicle upon whichthe headlight is mounted.

The invention will be more particularly described with reference to theappended drawings, wherein:

Fig. 1 is a vertical sectional view taken through the axis of aheadlight embodying features of the present invention;

Fig. 2 is a perspective view of the adjustable lightbeam directingelement of the headlight shown in Fig. l, the element having, however, asmaller circumference than the corresponding element in Fig. l but theother relative dimensions being not at the same scale.

Fig. 3a is a fragmentary view on an enlarged scale of one form of theblades or lamina which make up the light-beam directing element shown inFig. l and Fig. 2;

Fig. 3b is a similar view of a modified form of the lamina; I

Fig. 3c is a like view of a further modified form of lamina;

Fig. 4a is an enlarged view showing one of the laminae of the elementshown in Figs. 1 and 2, with the paths of the light rays being indicateddiagrammatically;

Fig. 4b is a similar View showing the paths taken by the light rays whenthe inclination of the lamina shown in Fig. 4a is changed;

Fig. 5 is a view similar to that shown in Figs. 4a and 4b illustratingthe paths of the rays through a lamina of modified proportions;

Fig. 6 is a fragmentary detailed view of an assembly of laminae having amodified form;

Fig. 7a is an elevational view of a modified form of light filament withassociated reflectors, and

Fig. 7b is an end View of the arrangement shown in Fig. 7a.

Referring to the drawings, and more particularly to Fig. l, theheadlight illustrated comprises a parabolic reflector 5' at the focus Fof which there is positioned the filament 4 of a lamp, the details ofthe lamp not being shown. It will be understood that in view of the factthat the filament has dimensions which are greater than zero, the beamof light rays emitted by the filament and reflected by the reflector 5will contain, in addition to rays which are parallel to the opticalaxis, ascending and descending rays as well. The amount of divergence ofthe total beam of the reflected rays which is of necessity not onlyupwardly and downwardly but also toward the sides, depends on thedimensions of the filament and on 2,834,874 Patented May 13, 1958 itsposition relatively to the focus F. The distance of focus F to a plane Pwhich is perpendicular to the axis A of the headlight defines thegeneratrix of the parabola of the reflector, providing the distancesfrom the focus to all of the points of the parabola are equal to thedistances from the plane P to these same points.

In the vertical plane of Fig. l the maximum divergence can be expressedby the angle through which the rays from the filament coil 4 are viewedfrom a point C of the reflector 5, a point assumed to be on the smallestcircumference which the filament can, in practice, illuminate when asection of the base of the paraboloid reflector is removed to permitpassage of the lamp socket. The diameter of the filament coil is, in theembodiment illustrated, of the vectoral ray F-C. The filament is,therefore, viewed from the point C through an angle of V of a radian or3 deg. 49 min. This value is sufficiently small to make possible theapplication of Lamberts law to the effect that the filament viewed fromthe point C would present a uniform luminous intensity, that is to say,that its luminous flux per unit surface would appear to be the same onthe periphery of the beam reaching point C as it would be in the middle.

Thus the beam of rays reflected by each of the points of the reflector,such as C, contains a horizontal ray R and two maximum divergent rays, Rupwardly and R downwardly, and it can be assumed that between theseextreme rays the intensity of the light flux is uniform.

But all of the circumferential portions of the reflector other than theone which contains the point C being farther removed from the focus F,such as those which contain the points B and D, the rays reflected atthese points are less divergent than the one which comes from the pointC, which fact is of importanceto the functioning of the elements of theheadlight to be described below, which elements are intended to preventthe blinding or dazzling of the drivers of approaching vehicles.

A cylindrical extension 6 projects in front of the reflector 5 and toextension 6 there is secured a frame 11 which supports the headlightglassiZ and supports a second frame 13 externally of the glass. In theannular portion of the reflector formed by the cylindrical extension 6there is disposed a rigid disk or circular block 9 of a compoundlaminated construction, to be described below, and this disk is mountedin such manner thatit can be inclined to varying degrees by rotationabout a horizontal axis 31 intersecting the axis A, suitable pivots, notshown, being provided in the extension 6 and engaged in blind holes 30in the disk 9. The disk 9 is formed from a series of strips, plates orlaminae '7 of a transparent, solid material, e. g. a resinous materialsuch as the polyacrylic resins known as Plexiglas and Lucite. The lamina'7 are positioned one on top of another to form a solid block, and theassembled laminae have the general configuration of a circular disk asshown in Fig. 2. The disk 9 is disposed in an annular mounting or frame29 in such manner that the lateral edges of the laminae 7 form the frontand back faces of the disk and are parallel to the axis 31. In theembodiment, illustrated, therefore, the cross section of each lamina isrectangular, but it could be in the form of a slightly-obliqueparallelogram.

The upper faces 7a of the laminae are polished to provide a mirror-likereflecting surface while the lower faces are scratched, furrowed orridged along lines parallel to the axis 31 so that they will not reflectbut will diffuse the rays which strike them. These ridges are obtainedby a substantially uniform cutting or shaping of the lower faces of thetransparent laminae to give a corrugated efiect which may have across-sectional form such as such, for example, in Figs. 3a, 3b and 3c.The corrugation 8a shown in Fig. 3a has a ratchet-like appearance, theflanks of each ridge being turned toward the interior of the headlight.The voids or open spaces between the apices of the ridges haveatriangular cross-section and the acute angle of the triangle isrepresented in Fig. 3a as 30 but this angle can be at least as small asthe inclination of the most strongly inclined rays issuing from thereflector. The teeth 8b of the furrowed surface shown in Fig. 3b are ofequilateral cross-sectional form, whereas the teeth 80 shown in Fig. 3care of a sinusoidal form.

An arm 32, secured to the annular frame 29, extends interiorally of thereflector and is articulated at 34 to an arm 35 which in turn isarticulated at its end to a horizontal shaft 36, which is supported by amember 37. The shaft 36 extends to the second headlight of the vehicle(not shown) and is similarly connected to a corresponding arm 35 of thesecond headlight. The second headlight is, of course, of the sameconstruction as the above-described first headlight. The shaft 35 entersthe headlight through a slot 40 in the reflector 5 and the member 37 ismounted for horizontal reciprocation and may be guided in a slideway orthe like and connected kinematically with an operating lever or rodpositioned within reach of the driver in order that the driver maychange the inclination of the disk 9 in either direction at will.Alternatively, this actuating arrangement may comprise a flexible cordor cable instead of the illustrated train of connecting rods and levers.

Each of the studs 27 projecting from the periphery of the extension 6 ofthe reflector 5 engage in slots 38 and ramps 39 formed in the frames 11and 13 for securing the frames to the reflector. The studs also passthrough a flanged hoop 25, the flange of which is fastened to the edge26 of a portion of the body of the vehicle, being received in a circularopening formed in this body portion. The fastening bolts (not shown) onthe edge 26 suitably engage in oblong holes in the form of circular arcswhich make possible the adjustment of the horizontal position of theaxis 31.

In Figs. 1, 4a and 4b the width of each of the laminae 7, measured fromthe front to the back of the block 9 is fifteen times its thickness, andgenerally speaking, widths of fourteen to forty, more particularlyfourteen to the thickness are particularly suitable. Consequently, inthe embodiment illustrated, the diagonals of a cross section of a laminaform with the faces of the lamina angles of A of a radian, the angleequal to that through which the filament 4 is viewed from the point C,and equal to twice the inclination of the maximum divergent rays R and Rwhich amounts to $4 of a radian.

For a fuller understanding of the course of the light rays shown in Fig.4 it is first necessary to consider Fig. 3a, in which there isillustrated one form of the corrugated or ridged faces 7b as Well as thecourse of rays f and f the inclinations of which havebeen greatlyexaggerated in order more clearly to show the refraction. It is to benoted that the lateral edges 70 of the laminae are not only plane butare polished as perfectly as possible. They can therefore be traversedby the light without causing the light to undergo any appreciablediffusion so that a ray f striking the lamina at 70 will enter thelamina in a given direction. If angle of incidence of the ray is i, itsangle of refraction r is such that sin r= (sin i)/(1.42), where 1.42 isthe index of refrac tion of the material forming the laminae relativelyto the index of refraction of air. The maximum value of the angle ofrefraction for this particular material, therefore, is such that sinr=1/1.42, which corresponds to an angle of about 44 deg. 37- min. 20sec. Since this angle is less than 45 deg, all of the rays which fall onthe face 7c at an angle of the same size as the angle designated i andwhich can after their refraction reach the face 7a undergo against thisface total reflection, this face being a surface of separation betweentwo media whose indices of refraction differ sufiiciently from eachother, as is the case when the lamina are formed from the polyacrylicresin Plexiglas which has an index of 1.42 relatively to the airimprisoned in the voids of the corrugations 8a. There is even greaterreason for the total reflection of the rays of very small inclinationcoming from the reflector, and this is possible even if a glue isinterposed between the laminae, provided that its index of refraction issufficiently small.

There is shown in Fig. 3a a ray which, after refraction, is arrested bythe face 7b where it is diffused by the flanks of the teeth which havebeen left rough by the shaping of the corrugations. This ray could alsobe absorbed more or less completely by the face 7b if a black or darkmaterial 7' were interposed in the spaces or voids between the teeth orridges of the corrugations.

In Figs. 4a, 4b and 5, wherein, for simplicity of illustration, thecorrugation of the lower faces is not represented, it is understood thatthe rays which strike these faces on the inside are arrested or diffusedas would be the case in practice with corrugated laminae.

In the horizontal position of the lamina, as shown in Fig. 4a, all ofthe horizontal rays R pass through the lamina directly. The rays R and Rof maximum inclination strike the lamina at angles i which are equal to54, radian but in the opposite direction. In penetrating into the laminathey are refracted and form with faces 7a and 7b equal angles 1' which,expressed in radians, have a value r=(1/30) (1.1.42)=l/42.6.

Thus those of these rays which penetrate into the lamina and just grazethe lower and the upper sharpedges of the ridges emerge from the laminaat the points e and f, the distances of which to the lower and to theupper face are equal and are 42.6 times smaller than the wide of thelamina. Since the width of the lamina is 15 times greater than itsthickness, this distance is 42.6/ 15 =2.84 times smaller than thethickness, of which, therefore, it is the fraction l/2.84=0.352.

In the drawing, R a are those of the rays R which strike the base of thelamina. From this it follows that the point e, the distance of which tothe upper edge of the lamina is the fraction 1O.352=0.648 of thethickness, marks the lower limit of a group of rays R which traverse thelamina directly and have at their emergence their initial inclination,in view of the fact that the faces of entrance and emission of thelamina are parallel. The upper limit of this group of rays is defined bya ray R b. It is the latter which is refracted in the lamina in a lineparallel to the internal path of the ray R a and emerges at the uppercorner of the emission face 41.

Another group of rays R having a thickness which is the fraction 0.35 ofthe thickness of the lamina, is comprised between the rays R b and R 0.Interiorly of the lamina this group of rays, refracted at its entrance,strikes the face 7a at an angle of 1/42.6 radian and is reflected bytotal reflection in a symmetrical direction toward the emission face 41,where, in passing a into the air, it is refracted downwardly, and takesan downwardly complement, on leaving the lamina, the group of rayscomprised between R 11 and R b of thoserays R which traverse the laminadirectly and which also occupy 65% of the thickness by reason ofsymmetry with the analogous group of rays R 11 to R b.

35% of the rays R are absorbed in the lower face, so

that parts of each of the categories of descending rays correspond tosmaller inclinations, which parts are smaller as the inclinations aresmaller. It is, therefore, more than 65% of all of the descending rayswhich are utilized in this position, and actually the quantity of theserays is approximately Likewise, all of the rays less ascending than therays R provide directly-utilized sheets of light which occupy more than65% of the thickness of the lamina and sheets of rays which are thinnerthan 35% of the lamina which are utilized after downward reflection.

In Fig. 4b, the lamina is inclined in such a way that the emission ofany ascending rays, no matter how slightly ascending, is prevented, sothat the emitted light does not glare in the eyes of any person in frontof the headlight whose eyes are higher than it is, not consideringreflection from a Wet road.

it should be noted that the emission of any ray which retains itsinclination cannot be prevented without inclining the laminasufficiently that no ray which is horizontal at the origin reaches theemission face 41 at a level lower than the upper edge of this face. Inpractice, therefore, it is necessary that all of thehorizontal raysundergo total reflection downwardly. For this purpose it isnecessarythat any ray R which penetrated into the lamina in grazing theupper edge 42 be refracted in such a way that it grazes the upper edgeof the face 41, that is to say, that it is refracted in the diagonalplane of the sheet inclined radian to the faces. It is thereforenecessary to calculate the angle of incidence 11 for which the angle ofrefraction has a value of A radian, and to give to the lamina aninclination to this angle of incidence. The lamina 7, the face of whichhas been prolonged by dashed lines L, is therefore inclined in Fig. 4bin such a way that its inclination is given by:

which corresponds to an angle of 5 deg. 25 min. Thus the entire group ofrays R which can strike the face 70 inclined between the edges 42 and 45strike the upper face 7a after refraction and is reflected downwardly atan angle equal to the imposed angle of refraction of radian. When thisgroup of rays reaches the emission face of the lamina, it is refracteddownwardly in passing into the air and takes an inclination symmetricalwith that which it had relatively to the lamina before its entrance. ltsabsolute inclination is, therefore, two times that of the lamina, thatis: 2(1/10.56)=1/5.28. If the headlight is one meter from the groundthis group of rays reaches the ground at a distance of 5.28 meters.

Since the sine of the angle of refraction increases proportionally withthe sine of the angle of incidence, and since all of the angles ofincidence of the ascending rays are necessarily greater than that of therays R it is clear that all of the refracted parts of these more or lessascending rays encounter the upper mirror-like face of the lamina andare reflected downwardly. For the rays R the inclination of ,4 radian ofwhich is assumed to be maximum, we have:

whence sin r =sin i (Il /n )=0.128/1.42=0.0902=1/11.1

which corresponds to about 5 deg. 10 min. and permits the refractedportion of the lower ray R a which strikes at a point 43' of the face 7ato be determined. By passing through the lower edge of the emission face41 of the lamina a parallel to this ray after its reflection at 43,there is found the point 44 of reflection at which will strike the rayRgd which is the highest of the rays R forming a well-defined utilizablegroup of descending rays at the emission face of the lamina. Those ofthe rays R which are higher are only utilized for diffuse illuminationof the lower corrugated face after their reflection against the part ofthe face 7a comprised between the points 44' and 45. All of the otherascending rays, which are less inclined, and which are not represented,will strike the face 7a at points comprised between points determinablein the same manner as the points 43' and 44', but which will be fartherapart the less they are inclined, so that there will be added to the twooutcoming sheets of rays R and R as many reflected sheets of rays asthere are different directions in the ascending rays coming from thereflector, and these sheets will have at their point of emission all ofthe thicknesses and all of the directions comprised between thethicknesses and the directions of the two sheets of rays R and R As tothe descending rays, their angles of incidence remain of the same signas those of the ascending rays, due to the fact that their maximuminclination is smaller than that of the lamina. The smallest of theseangles of incidence is that of the rays R given by:

sin i =1/lO.56l/3O= Accordingly, the angle of refraction r iscalculated: sin r =0.0604/1.42=0.0426=l/23.5, whence r =2 deg. 26 min.

By passing through the upper edge of the face of departure 41 a parallelto the refracted lower ray R a there is determined the thickness of anon-negligible group of those rays R which depart under their initialinclination of radian downwardly, and reach the ground at a distance of30 meters. On this sheet of light there are superposed other thinnersheets of rays which are less descending than the rays R but depart witha very small downward inclination. These other light sheets, therefore,illuminate the road beyond 30 meters. Their thicknesses are fractions ofthat of the lamina and the differences between these fractions and theunit are the relative thicknesses of the number of sheets of light thatstrike the face 7a at angles comprised between the values of r and r sothat their final inclinations are all smaller than the final inclinationof the rays R but nevertheless larger than that of the lamina, whichthey exceed at least by the value of i The thickness of the representedstratum of departure of the rays R is the fraction 0.36 of those of thesheet.

There is therefore obtained, in a position which prevents blinding ofoncoming drivers, a significant beam of downwardly reflected rays whichilluminates the road from 5.28 to 6.40 meters, and another descendingbeam of rays, not reflected, which reaches the ground at 30 meters andbeyond.

For the purpose of modifying the relative importance of these two beamsin such a way as to reinforce the longcarrying beam and to decreasetheir divergence by elevating the lower beam, we can decrease thethickness of the laminae relatively to their width. For example, for awidth of 30 mm. there can be used a thickness of 1.0 mm., instead of the2.0 mm. which corresponds to the ratio 1/15 of Figures 1 and 4 of thedrawing, for the purpose of obtaining the ratio 1/30. Generallyspeaking, the thicknesses of the laminae may vary from a fraction of amillimeter, e. g. mm. to about three millimeters.

Fig. 5 represents the principal effects obtained under those conditionswhen the lamina has the inclination which makes the angle of refractionof the horizontal rays equal to radian. The inclination of the lamina isthen half that which it is in Figure 4b, since: sin i=1.42/ 30:1/ 21.1.The angles of incidence of the rays R and R become: sin i:l/21.l|1/30=51.l/633=l/l2.4, and

whence we have for the corresponding angles of refraction: sin r=(l)/(12.4 l.42)=l/l7.6, and

The sheet of rays R which strikes the designatedby43"'and 44" arecloseritogether than the corresponding points'43' and'44', sothat theutilized por'tion' ofthe ascending rays. at the origin isdecreased tothe profit of the portion of .the descending rays which are finallyutilized with Itheir initial inclination. The most important ofthesheets of rays r'flected' downwardly, that of the initially-horizontalraysRgs'till has aLfai'rlygreat'final-inclination, amounting to twicethe inclination ofthe lamina, thatis, 171056, so that it reaches theground at about ten meters from'the vehicle.

The phenomenonof theidilfrac'tionofthe rays which graze the edge ofa'su'rface, which is neglected in the above discussion which is based onthe'appro'xim'ate' hyp'othesis ofthe rectilinearpropagation of light,has the effect'of merging togetherrthe edgesof theseveral' sheets oflight considered above, so that thezhorizontallimit of these sheets doesnot remain clear at a great distance from the headlight. Accordingly,.-a:person positioned in front-ofthe headlight, and-whose:eyes. are higherthan it,'.-may receive upwardly-diffracted rays,even if the conditionsof. Figure are satisfied. Moreover,.if we apply to i the diffractedrays. the. theorem: of inverse propagation of rays, we see that theperson,.instead of seeing the lower furrowed and diffusing face ofalamina inthe direction ofdiffracted rays terminating: at hiseyeand'grazing the upper edge of the lamina; sees these :rays as. comingfrom the reflector andthe filament. FI0I1'1IIhlS'it follows that therestill exists a certain amount ofglare although it is much smaller thanthat which-the same person would have experienced before the inclinationof the disk. Specifically, these diffracted rays belong .to. the fringesof the beam coming from each of the laminae, and these fringes are lessluminous than the principal beam.

Thus, the driver'ofa vehicleapproachingzthe headlight, which'hehasfirstseenfrom a distance in. the position of'Figure 4a at fullillumination, clearly perceives a decrease in the glare of the.light atthejinstant that the disk is'. inclined as.in Figure v5,.although he maystill receive some diffracted rays which have passed above the height ofthe headlight. This residual glaredue to the diffractionv diminishesrapidly" as: the "two vehicles come closer tozeach other,'because hisdue to the fringes of light which are more and more elevated and henceless and less luminous. Finally, itzdisappears completely at afdistaneeof about meters :Itis an advantage from the physiologicalviewpoint-:ihat. the .eauseof the glare decreases only rgradually.

i The driverof the vehiclerwith the headlight described up to this pointmay find.that the illumination of the road at "meters and beyond-is lessthan between 10 and 20 meters. This'may be :due tothe fact that theupperbeamis lessstrong.than'Fthe others, or thatits diffraction increaseswith increasingzdistance, orespecially that it is at least as-divergenthorizontally as vertically while the widtlr'ofithe road is consta'nh sothatat the distance at which the luminous beam becomes wider than theroad only a part of it falls'on'fthe road. The impression of lessillumination at'greatidistances can be'still further reinforcedphysiologically if the road'is really more'illumina'ted atshorter-distances, because the eye, accommodating itself ofthis.greater-illumination, cannotaccommodate itself to the weakerdistant illumination.

Figures 6 and 7"show'modified forms of construction intended to improve:these conditions.

Figure 6 shows -the front portion ofthe laminae 7 inclined as in Figure5, and modified in a manner to prevent the rays from'being' diffractedupwardly in grazing the-rupper-edges of thefront faces, which edges arein theembodimentof Figures I and 4' the lines of intersection-of'the'front faces andthe-upper faces 7a. In'the modified form of Figure 6 thisedge is replaced by the intersection of theface 7a and a bevel 46cutting the upperfront corner of each of the laminae 7. A horizontalline H shows the downwardiinclination of a rayR less inclined than .thefaces 17a. andi7b. Theanalogous upper rays are all reflected byjtheface"7a. The ray shown, is takento be the first of thosehavinganon-reflecteddirection, that is, one which,'in.the absence of thebevel 46, would graze the edge of. the mirror-like face without touchingit, and which would be diifracteiupwardly. This diffraction is-avoidedbecause the ray strikes at the level of the bevel 46 and forms, with theperpendicular N to the bevel at the point of incidence, an angleawhichis smaller-than the maximum angle ofrefraction of, a ray passingfromtheair intothe materialofrwhich the lamina '7 is made. This ray istherefore, refracted in passing intotheair in forming with theabove-mentioned perpendicular-an angle ,8 which is' less than deg.Thesame thing would-also be,true of rays parallel, with the ,faces 7aand tangential to these faces or .very, nearly.s0. The refractedportions of ,such rays passing into;the air, are, therefore, spacedat'their. origin from'the. edge 47,,which the face7brformswith-the front.face. Theirdifiraction can therefore be diminished.or,annulled,, and,if it is not diminished, ituno longerhas a blinding or, glaring effect,in view' of the factthatthese rays are, nowsteeply inclined downwardly.

"The bevel 46,.instead ,ofbeing polished .asis thecase above, can beunpolished. In this case, it.wo,uld thenube the diifusiomof. the ,lightwhich it received which would prevent diffraction.

Fig. 7a shows a modified arrangement of the filament 4 inaside-elevation view -and"-Fig. 7b shows-it-in end view.' This. filamentis disposed along theaxis A of-the reflector, and extends azsubstantialdistance on eachside of the .focus relativelytothe averageeffectivevectoral ray of the reflector, so that :the rays coming fromits ends are reflected along inclinations equal in absolute value tothat which the, laminae 7 .have-twhenithey, satisfy the conditions ofFigures 4b-and 5.

A cylindricalreflectorAS, similar-to those'which are known inlampshaving-two,filam ents, is disposed below the front partilaof thefilament coaxiallylwith the axis A but .extendingover onlyv a fractionof the length of the filament. An .identical reflector 49 .is;disposed,symmetrically above the other end..4b of .the same filament.

The purpose of this arrangement is, that the two upper and lower halvesof the reflectorfurnishmore rays refiected downwardly.thanascendingrays,- since-thelatter can only come from the, central partofthefilament, at the same" time as thedescending rays. Thisarrangement isdictated by: the characteristics, of the-actionshown in Figure 5, wherehis seen that,thelong-carrying-beam is formed byinitially-descendingrays which traverse the lamina 7 directly withoutundergoing reflectiondownwardly. It should be noted that the filament 4,of Figure 7 is constantly energized regardless of 'the' position ofthedisk 729.

In the event that it is desired to diminish the luminosity of thefurrowed faces 717 by. the interposition of a dark coating Whose bindingmaterial has an index of refraction .very little less than that of thesheets, there can be placed in. contact. with the polished .faces7a..thin.imetal foils, .e., g. aluminum foils 8'.of a .thicknessless;than :mm. .Alternatively, thefaces7a; can be, metallized directly,vin..accordanee .with known -metallizing techniques. However, thetotaltrefiectiontwithout this modification .is:still assured with .the'small inclinations .pro-

videcl for the rays ifthe index of refraction rofzthe hindingmaterial isonly slightly less :than that:of-.the laminae.

The two parts 4:: and 4b of therfilament-lofFigure7a, 1

or two corresponding .separate' filaments, could .be separated byaspace: containing .thezfocus, and in which there is mounted. a.transverseand vhorizontal filament having a diameter'selected insuchaway as to. furnish animportant flux of rays with verysmalldivergence-upwardly and downwardly, and, having aalengthfwhich ishof the same order of magnitude as therdiameter. This filament wouldpreferably be fed at .thesame. time .as. the. axial 9 filament, whilebeing mounted either in series or in parallel therewith. The reflectorcould be limited to a sector of a paraboloid of revolution.

A lens could be placed in front of the light source with its focus atthe light source in such a way that it transforms the conical flux intoa parallel beam. The lens could also be formed as an integral part ofthe lamp bulb.

It will be apparent that various other changes and modifications may bemade in the embodiments of the invention above-described and shown inthe drawings in addition to those indicated above. For example, in theembodiment of Fig. 6, the lower edge of the front face of each laminamay be beveled as well as the upper edge. It will be understood that,insofar as they are not mutually incompatible, the various features anddetails of construction of the several embodiments shown and describedare interchangeable with one another. It is intended, therefore, thatall matter contained in the foregoing description and in the drawingsshall be interpreted as illustrative only and not as limitative of theinvention.

This application is a continuation-in-part of co-pending application,Serial No. 210,962, filed February 14, 1951, and now abandoned.

What we claim and desire to secure by Letters Patent is:

1. A vehicle headlight comprising, in combination, a parabolicreflector, a source of light centered at the focus of said reflector,and means for modifying the paths of the light rays leaving said lightsource and reflector for the purpose of diminishing the glaring effectproduced by the rays upon the driver of an approaching vehicle, saidmeans comprising a front extension to said reflector, a rigid diskformed from a plurality of laminae of a solid transparent material, saidlaminae being assembled with their lateral edges forming the front andrear faces of the disk, a frame holding the assembly of laminae todefine said disk, said disk being sufliciently large that it receives atleast the greater part of the light rays reflected by the reflector,said laminae having their upper faces polished and their lower facesfurrowed in a direction parallel to their edges, said disk being mountedfor rotation about a horizontal axis parallel with its faces and thefaces of the said laminae, said axis being perpendicular to the opticalaxis of the headlight, said laminae having a thickness comprised betweenA and ,4 of their width measured in a vertical plane parallel to theoptical axis and having their front and rear lateral edges polished overat least the greater part of their 10 height, actuating means foradjusting the angular position of the disk in said extension.

2. A vehicle headlight as defined in claim 1, wherein dark material isinterposed between the laminae and wherein metal foils are interposedbetween the upper faces of the laminae and said dark material.

3. A vehicle headlight as defined in claim 1, wherein the front face ofeach of the laminae is formed with a bevel at its upper edge, said bevelcutting the plane of the upper face at an acute angle greater than 45degrees, said bevel occupying a minor proportion of the height of thefront face of said laminae.

4. vehicle headlight as defined in claim 3, wherein said bevel occupiesthe thickness of the laminae.

5. A vehicle headlight as defined in claim 3, wherein the bevel ispolished.

6. A vehicle headlight as defined in claim 1, wherein the light sourceis a lamp having a filament directed along the axis of revolution of theparabolic reflector and extends by amounts substantially equal beforeand behind the focus of the reflector, and wherein two cylindricalreflectors are symmetrically disposed along said axis, one below thefront half of the said filament, and the other above the rear half, andextending over equal portions of each of the filament halves inwardlyfrom opposite ends of the filament.

7. A headlight for a motor vehicle as defined in claim 1, wherein saidplurality of solid transparent laminae are formed from a syntheticresinous material.

8. A headlight as defined in claim 1, wherein said laminae have athickness within the range of a fraction of a millimeter to 3millimeters and a width which is fourteen to seventeen times saidthickness.

References Cited in the file of this patent UNITED STATES PATENTS1,100,484 Inman June 16, 1914 1,269,548 Palmer June 11, 1918 1,442,463Bowman Jan. 16, 1923 1,537,219 Berg May 12, 1925 1,633,387 Shippey eta1. June 21, 1927 2,539,927 Ramminger Jan. 30, 1951 FOREIGN PATENTS199,033 Great Britain 1924 641,093 France Apr. 10, 1928 518,675 GreatBritain Mar. 5, 1940

